1. Field of the Invention
The present invention relates to a sheet punching device for cutting a hole in a sheet, and an image forming apparatus, such as a copying machine, a printer, a facsimile machine, and a composite apparatus including the foregoing devices, provided with the sheet punching device.
2. Related Background Art
Up to now, a sheet punching device includes punches and dies of the number corresponding to the number of holes to be cut in a sheet and cuts the holes in the sheet while the punches are entering die holes, respectively.
However, the conventional sheet punching device is equipped with only the combination of the paired punches and dies of the same number as that of the holes to be cut in the sheet. For that reason, because the punches and the dies are quickly worn, the punches and the dies must be frequently replaced by new ones, resulting in a low efficiency of punching the sheet.
Also, because the number of holes to be cut in the sheet is different depending on the respective countries, if the conventional sheet punching device is adapted to a standard of some countries, it can not be adapted to a standard of other countries.
For example, in Japan, there are many cases in which two holes are cut in the sheet, and the sheet punching device that cuts two holes in the sheet cannot be adapted to such standard as of U.S.A. in which three holes are cut in the sheet.
Under the above circumstances, the operation of the sheet punching device is suspended and the punches and the dies must be replaced by new ones every time the number of holes is changed, thus degrading the punching efficiency.
Also, since an image forming apparatus with the conventional sheet punching device is low in the punching efficiency of the sheet punching device, the efficiency of forming an image on the sheet is low.